Bunching onions, or spring onions, are perennial, non-bulb forming onions with a mild taste. Unless you are after the honking humongous onion bulbs for burger slices, bunching onions are a great way to go. You plant once, and never again! Remember, perennial. I guess you could call them "permanent green onions," since they won't grow out of that green onion stage.
Last year I started Welsh onions, Allium fistulosum, from seed in wintersowing containers.
I planted three in my raised bed #1, for mostly ornamental reasons, but a few green onions now and again are not unwelcome!
Being Welsh onions, which by the way do not originate in Wales, but China ("Welsh" being an old world word meaning "foreign") are new to care for this year, so I was unsure what to do for winter prep. It's easy to find information on planting them, caring for them, harvesting them, etc. but not how to treat them as the perennial allium they are. I found one video online trying to address that same issue. His onions were grown as perennial vegetable crops. I guess you could say, just treat them as you do any allium, cutting back the old flower stems, and gathering up any dead leaves at the end of the season... except these do not have an end season in some zones, so...
I had already cut my bunching onions down in June. Within a matter of days you could see new growth! If you have ever used half an onion, and stored the rest in the refrigerator, you know how how quickly they sprout. Place the white end of a green onion in water and it grows too.
They were all over the place a few weeks ago, in need of another trim. They are no longer just three!